I have made 5, 6, 7 and 8 fold bellows for 3 row anglos. My Jones has 8 fold and it developed a rather open bellows playing style, hands apart, which I have to be aware of if i am playing on lesser fold instruments. The Jeffries has 7 fold, and they seem just right for my straight along the row style, with an attempt to walk the bass (I am not a particularly good player). The Lachenal has 6, and sometimes I find myself just about to run out of air, especially if I play the bass, another Lachenal with 5 folds, the first set of bellows I ever built, does run out of air, especially if I touch the bass, and is a real menace.
My advice, especially if you play in the set keys straight along the rows (not across in the Irish style) is no less than 6 folds. (I have sat is sessions with some pretty nifty Irish players who barely seem to move the bellows, while I am pumping like an air gulping guppy ... it all in the style, and if you are an old accordion player who 'omph cha's' the bass a lot of air is used)